Role of chain architecture in the solution phase assembly and thermoreversibility of aqueous PNIPAM/silyl methacrylate copolymers,Polymer Chemistry

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Role of chain architecture in the solution phase assembly and thermoreversibility of aqueous PNIPAM/silyl methacrylate copolymers
Polymer Chemistry ( IF 4.1 ) Pub Date : 2022-06-08 , DOI: 10.1039/d2py00254j
Jason D Linn ₁ , Lucy Liberman ₁ , Christopher A P Neal ₁ , Michelle A Calabrese ₁

Affiliation

Stimuli-responsive polymers functionalized with reactive inorganic groups enable creation of macromolecular structures such as hydrogels, micelles, and coatings that demonstrate smart behavior. Prior studies using poly(N-isopropyl acrylamide-co-3-(trimethoxysilyl)propyl methacrylate) (P(NIPAM-co-TMA)) have stabilized micelles and produced functional nanoscale coatings; however, such systems show limited responsiveness over multiple thermal cycles. Here, polymer architecture and TMA content are connected to the aqueous self-assembly, optical response, and thermoreversibility of two distinct types of PNIPAM/TMA copolymers: random P(NIPAM-co-TMA), and a ‘blocky-functionalized’ copolymer where TMA is localized to one portion of the chain, P(NIPAM-b-NIPAM-co-TMA). Aqueous solution behavior characterized via cloud point testing (CPT), dynamic light scattering (DLS), and variable-temperature nuclear magnetic resonance spectroscopy (NMR) demonstrates that thermoresponsiveness and thermoreversibility over multiple cycles is a strong function of polymer configuration and TMA content. Despite low TMA content (≤2 mol%), blocky-functionalized copolymers assemble into small, well-ordered structures above the cloud point that lead to distinct transmittance behaviors and stimuli-responsiveness over multiple cycles. Conversely, random copolymers form disordered aggregates at elevated temperatures, and only exhibit thermoreversibility at negligible TMA fractions (0.5 mol%); higher TMA content leads to irreversible structure formation. This understanding of the architectural and assembly effects on the thermal cyclability of aqueous PNIPAM-co-TMA can be used to improve the scalability of responsive polymer applications requiring thermoreversible behavior, including sensing, separations, and functional coatings.

中文翻译：

链结构在水性 PNIPAM/甲基丙烯酸甲硅烷酯共聚物的溶液相组装和热可逆性中的作用

用反应性无机基团功能化的刺激响应聚合物能够创建具有智能行为的大分子结构，例如水凝胶、胶束和涂层。先前的研究使用聚（ N-异丙基丙烯酰胺-co -3-（三甲氧基甲硅烷基）丙基甲基丙烯酸酯）（P（NIPAM- co -TMA））稳定了胶束并产生了功能性纳米级涂层；然而，此类系统对多个热循环的响应能力有限。这里，聚合物结构和TMA含量与两种不同类型的PNIPAM/TMA共聚物的水性自组装、光学响应和热可逆性相关：无规P(NIPAM- co -TMA)和“嵌段官能化”共聚物，其中TMA 定位于链的一部分，P(NIPAM- b -NIPAM- co -TMA)。通过浊点测试 (CPT)、动态光散射 (DLS) 和变温核磁共振光谱 (NMR) 表征的水溶液行为表明，多个循环的热响应性和热可逆性是聚合物构型和 TMA 含量的重要函数。尽管TMA含量较低（≤2 mol%），嵌段官能化共聚物在浊点以上组装成小而有序的结构，从而在多个循环中产生独特的透射行为和刺激响应性。相反，无规共聚物在高温下形成无序聚集体，并且仅在可忽略的 TMA 分数（0.5 mol%）下表现出热可逆性；较高的TMA含量会导致不可逆结构的形成。了解结构和组装对水性 PNIPAM- co -TMA 热循环性的影响，可用于提高需要热可逆行为的响应聚合物应用的可扩展性，包括传感、分离和功能涂层。

更新日期：2022-06-08

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